The invention concerns a racket for ball games, in particular a tennis racket, having a stringing surface which is provided in a stringing frame and which comprises mutually crossing strings which are possibly sections of at least one longer string portion. The invention also concerns the configuration of a string portion or a string per se.
Such a tennis racket, as is described for example in the present applicant's German patent specification No 34 34 898, with a longest string of 330 mm, which extends parallel to the longitudinal axis of the racket, is strung for example at a tension of about 30 kg. That loading is preset on a tensioning machine. If that string were to be measured in the strung racket, for example using a wire strain gauge, the actual tension is always set to a substantially lower value as the string yields due to the material used, in itself or due to the mechanical play in the machines and the tensioning collet. On the basis of experience, the actual value is about 70% of the set tension value, that is to say in this case about 21 kg.
Now it is possible to select for example a 1.3 mm thick gut string which, assuming ball impact, absorbs 2 kg. It is therefore tightened from 21 to 23 kg and the increase in stretch is 8.25%-7.5%, that is to say 0.75%, relative to the length of 330 mm, consequently 2.47 mm. The string which is most closely adjacent thereto in parallel relationship is still 320 mm in length and would only want to increase in length by 2.4 mm. And in actual fact, if all strings are intended to yield to the same degree, it would have to be less heavily tensioned.
A disadvantage in regard to those considerations is that, with such a mode of stringing, the stringing machine must be set to a new value for each string length. In addition, it is then no longer possible in practice to rely on the relatively simple stringing instructions from the individual manufacturers.
Also known in the state of the art is a racket stringing arrangement comprising a plurality of longitudinal and transverse strings of thicker cross-section, which form the middle of the racket, and thinner strings which extend outside the usual impact area, that is to say in the corner surfaces defined by the cross-shaped surface formed by gut strings, and which consist of a different material, in order to take account of the increased loading in the impact area or "sweet spot", by virtue of thicker strings, and in order to have to replace only the strings in the sweet spot, in the event of wear.
In consideration of those factors, the inventor set himself the aim of providing an ideal stringing arrangement for a racket of the kind set forth above, which avoids the above-discussed measures. In addition the invention seeks to provide that the striking performance of the racket in general is improved.